Ovulation: understanding its role and impact on a woman's fertility

What is ovulation? What role does it play in the menstrual cycle? 

Ovulation is a key stage of the menstrual cycle, during which a mature egg, called an oocyte, is released from one of the ovaries. This essential biological process plays a central role in the female menstrual cycle.

The menstrual cycle has four main phases:

• The follicular phase: begins on the first day of menstruation and ends with ovulation. Under the action of FSH (follicle stimulating hormone), several follicles mature, but only one, the dominant one, reaches maturity.
  
• Ovulation: a spike in LH (luteinising hormone) causes the dominant follicle to rupture and release an egg that can be fertilised for 12 to 24 hours.
• The luteal phase: the ruptured follicle becomes a corpus luteum, secreting progesterone to prepare the uterus for pregnancy. In the absence of fertilisation, it degenerates, causing hormones levels to fall.
  
• Menstruation: The uterine lining detaches, marking the start of a new cycle.
  

Ovulation is a process during which an egg moves into the fallopian tube to be fertilised by a sperm. It usually occurs on the 14th day of a 28-day cycle, but cycles can vary in length from 26 to 32 days depending on the woman.

Ovulation occurs when LH, produced by the pituitary gland, reaches a high peak, stimulated by the increased levels of oestrogen in the dominant follicle. The dominant follicle releases the egg, which is captured by the fringes of the Fallopian tube, where it can be fertilised.

The ovulation process takes approximately 24 to 36 hours, but the released egg remains fertilisable for a shorter period, generally 12 to 24 hours. If the egg meets a sperm cell in the fallopian tube during this time, fertilisation can take place, giving rise to an egg cell.

What are the symptoms of ovulation? 

Some women may experience symptoms related to ovulation such as:

• A light pain in the lower abdomen, known as Mittelschmerz,
• A change in the cervical mucus, which becomes clearer and more elastic to facilitate the passage of the sperm,
  
• An increase in basal body temperature, which rises slightly after ovulation,
  
• Increased sensitivity of the breasts or nipples, which may become more sensitive or painful,
  
• A change in the cervix, which may become softer, higher and slightly open,
  
• An increase in libido, as the body instinctively favours reproduction,
  
• Slight blood loss or spotting, often linked to the rupture of the follicle,
  
• Increased sensitivity to odours, which may be linked to hormonal changes.

How does ovulation affect fertility?  

Ovulation is an essential phase in the reproductive process, as it marks the moment when conception is possible. Regular ovulation is an indicator of good reproductive health, and observing it can be useful both for planning a pregnancy and for avoiding one.

Regular cycles generally indicate a good hormonal balance, often linked to satisfactory overall health. Conversely, irregular cycles may indicate underlying disorders that should be explored, even if there are no fertility-related issues.

What are ovulation disorders? 

Women may find it difficult to conceive if their ovaries do not release an egg each month, as is usually the case during a normal menstrual cycle.

If a couple finds it difficult to conceive, checking ovulation with special tests is the first thing that can be done. The simplest method is the temperature curve, which detects a slight rise of temperature after ovulation. A post-coital test can also be carried out to analyse the cervical mucus and its interaction with the spermatozoa. A pelvic ultrasound is used to check for ovarian abnormalities, and hormone levels are measured to assess the quality of ovulation.

Several factors can affect the ovulation process:

• Stress: whether physical or emotional, stress can upset hormonal balance and disrupt ovulation,
  
• Weight: too little or too much body weight can unbalance hormone levels, leading to irregular ovulation,
  
• Excessive exercise: intensive physical activity can cause hormonal disturbances and alter the ovulation,
  
• Unbalanced diet: this can also disrupt ovulation cycles.
  

Anovulation (absence of ovulation) or dysovulation (ovulation disorder) are frequent causes of infertility, often linked to a variety of underlying causes.

In addition, certain health problems can also disrupt the ovulation process, including :

Polycystic ovary syndrome (PCOS) 

In polycystic ovary syndrome (PCOS), immature follicles in the ovaries fail to release eggs and accumulate, upsetting the hormonal balance. This leads to irregular cycles and difficulty conceiving.

Endometriosis 

Endometriosis affects around 10% of women. Endometrial-like tissue in the peritoneal cavity disrupts the quality of ovarian follicles and impairs embryo implantation.

Ovarian insufficiency 

Ovarian insufficiency, also called ovarian failure, is the absence of ovulation and menstruation. It can be primary (absence of puberty and menstruation) or secondary (early menopause), with rapid degeneration of the follicles. This leads to a fall in hormones levels and symptoms similar to the menopause.

Hyperprolactinemia  

Prolactin, produced by the pituitary gland during pregnancy, supports breastfeeding. If it is secreted abnormally outside pregnancy, this is known as hyperprolactinaemia, and it disrupts ovulation, causing long cycles or the cessation of menstruation.

Hormonal disorders  

Thyroid disorders, whether caused by hypothyroidism (too little hormone) or hyperthyroidism (too much hormone), can interfere with ovulation. Hypothyroidism can lead to irregular cycles or no ovulation, while hyperthyroidism can cause short or irregular cycles.

Bilateral tubal stenosis 

This is a reduction in the permeability of the fallopian tubes, blocking the passage of the sperm towards the egg. It is often caused by an infection, such as Chlamydia, a common STD. It is a major cause of infertility.

Uterin abnormalities 

The absence of a uterus (Rokitanski syndrome, androgen resistance syndrome) or uterine malformations, as well as endometrial polyps or uterine fibroids, are responsible for infertility.

Other causes of ovulation problems include diabetes, obesity, depression, and certain medications, particularly oestrogens, progestins and certain antidepressants.

How are ovulation disorders treated? 

Treatment for ovulation disorders depends on the underlying cause. It may include drug treatments such as letrozole, clomiphene or human gonadotropins to stimulate ovulation, depending on the specific disorder.

If medication does not work, surgery may be necessary:

• Ovarian drilling: this procedure involves drilling holes in the ovaries to remove excess follicles and restore ovulation. It is carried out by laparoscopy under general anaesthesia.
  
• In Vitro Maturation (IVM): for some women, immature follicles are removed under anaesthesia and matured in the laboratory.

How to correctly monitor your ovulation? 

There are several methods available for monitoring and identifying ovulation:

• The calendar method: this involves noting the first day of menstruation in each cycle and counting around 14 days after it to estimate the likely date of ovulation.
  
• The basal body temperature graph: by measuring the temperature each morning before getting up, you can detect a slight rise, indicating recent ovulation.
  
• Ovulation test kits: these tests detect luteinising hormone (LH) in the urine, the level of which rises just before ovulation.
  
• Cervical mucus observation: analysing changes in the texture and appearance of cervical mucus can help predict ovulation.
  
• In addition, healthcare professionals use blood tests to measure hormone levels and ultrasound scans to monitor the growth of ovarian follicles and confirm ovulation. 

Finally, there are a number of digital tools and applications available to help you easily calculate and monitor your ovulation.

To optimise ovulation, it is advisable to eat a balanced diet, rich in essential nutrients such as zinc and vitamins B. It is also important to maintain a healthy weight, as being overweight or underweight can disrupt ovulation.

In the event of problems, it is better to make an appointment with a healthcare professional, such as an endocrinologist or a gynaecologist, who can suggest appropriate treatments.